Role of CxxC-finger protein 1 in establishing mouse oocyte epigenetic landscapes

During oogenesis, oocytes gain competence and subsequently undergo meiotic maturation and prepare for embryonic development; trimethylated histone H3 on lysine-4 (H3K4me3) mediates a wide range of nuclear events during these processes. Oocyte-specific knockout of CxxC-finger protein 1 (CXXC1, also known as CFP1) impairs H3K4me3 accumulation and causes changes in chromatin configurations. This study investigated the changes in genomic H3K4me3 landscapes in oocytes with Cxxc1 knockout and the effects on other epigenetic factors such as the DNA methylation, H3K27me3, H2AK119ub1 and H3K36me3. H3K4me3 is overall decreased after knocking out Cxxc1, including both the promoter region and the gene body. CXXC1 and MLL2, which is another histone H3 methyltransferase, have nonoverlapping roles in mediating H3K4 trimethylation during oogenesis. Cxxc1 deletion caused a decrease in DNA methylation levels and affected H3K27me3 and H2AK119ub1 distributions, particularly at regions with high DNA methylation levels. The changes in epigenetic networks implicated by Cxxc1 deletion were correlated with the transcriptional changes in genes in the corresponding genomic regions. This study elucidates the epigenetic changes underlying the phenotypes and molecular defects in oocytes with deleted Cxxc1 and highlights the role of CXXC1 in orchestrating multiple factors that are involved in establishing the appropriate epigenetic states of maternal genome.

Epigenetic initiation of the TH17 differentiation program is promoted by Cxxc finger protein 1

IL-6/STAT3 signaling is known to initiate the TH17 differentiation program, but the upstream regulatory mechanisms remain minimally explored. Here, we show that Cxxc finger protein 1 (Cxxc1) promoted the generation of TH17 cells as an epigenetic regulator and prevented their differentiation into Treg cells. Mice with a T cell–specific deletion of Cxxc1 were protected from experimental autoimmune encephalomyelitis and were more susceptible to Citrobacter rodentium infection. Cxxc1 deficiency decreased IL-6Rα expression and impeded IL-6/STAT3 signaling, whereas the overexpression of IL-6Rα could partially reverse the defects in Cxxc1-deficient TH17 cells in vitro and in vivo. Genome-wide occupancy analysis revealed that Cxxc1 bound to Il6rα gene loci by maintaining the appropriate H3K4me3 modification of its promoter. Therefore, these data highlight that Cxxc1 as a key regulator governs the balance between TH17 and Treg cells by controlling the expression of IL-6Rα, which affects IL-6/STAT3 signaling and has an impact on TH17-related autoimmune diseases.

ERK2 phosphorylates the epigenetic regulator CXXC-finger protein 1 (CFP1)

BackgroundThe Ras-Raf-MEK-ERK signaling pathway is essential for proper development and homeostatic regulation in eukaryotic cells and underlies progression of several types of cancer. Many pathway functions are performed by extracellular signal-regulated kinase (ERK)1 and 2 (ERK1/2), serine/threonine protein kinases of the mitogen-activated protein kinase (MAPK) family that interact with a large number of substrates and are highly active in the nucleus.ResultsWe identified the epigenetic regulator CXXC-finger protein 1 (CFP1) as a protein that interacts with ERK2 on chromatin. CFP1 is involved in multiple aspects of chromatin regulation, including histone methylation and DNA methylation. Here, we demonstrate the overlapping roles for ERK1/2 and CFP1 in regulation of immediate early gene (IEG) induction. Our work suggests multiple modes of co-regulation and demonstrates that CFP1 is required for an optimal signal-dependent response. We also show that CFP1 is an ERK2 substrate in vitro and identify several phosphorylation sites. Furthermore, we provide evidence that Su(var)3-9, Enhancer-of-zeste and Trithorax (Set)1b, a CFP1-interacting histone methylase, is phosphorylated by ERK2 and is regulated by CFP1.ConclusionOur work highlights ERK1/2 interactions with chromatin regulators that contribute to MAPK signaling diversity in the nucleus.

The epigenetic regulator Cfp1

Numerous epigenetic modifications have been identified and correlated with transcriptionally active euchromatin or repressed heterochromatin and many enzymes responsible for the addition and removal of these marks have been characterized. However, less is known regarding how these enzymes are regulated and targeted to appropriate genomic locations. Mammalian CXXC finger protein 1 is an epigenetic regulator that was originally identified as a protein that binds specifically to any DNA sequence containing an unmethylated CpG dinucleotide. Mouse embryos lacking CXXC finger protein 1 die prior to gastrulation, and embryonic stem cells lacking CXXC finger protein 1 are viable but are unable to achieve cellular differentiation and lineage commitment. CXXC finger protein 1 is a regulator of both cytosine and histone methylation. It physically interacts with DNA methyltransferase 1 and facilitates maintenance cytosine methylation. Rescue studies reveal that CXXC finger protein 1 contains redundant functional domains that are sufficient to support cellular differentiation and proper levels of cytosine methylation. CXXC finger protein 1 is also a component of the Setd1 histone H3-Lys4 methyltransferase complexes and functions to target these enzymes to unmethylated CpG islands. Depletion of CXXC finger protein 1 leads to loss of histone H3-Lys4 tri-methylation at CpG islands and inappropriate drifting of this euchromatin mark into areas of hetero-chromatin. Thus, one function of CXXC finger protein 1 is to serve as an effector protein that interprets cytosine methylation patterns and facilitates crosstalk with histone-modifying enzymes.